We don't see a lot of mold in the Phoenix area where I work in commercial janitorial, as mold likes wet places; most building here have little problem with wet foundation, walls or attic. But where there is an active moisture source - think a floor drain, a pipe leak in a restroom wall, a blockage in the drain line
from the air conditioning unit - we have a problem, just like anyone else.
Some people are allergic to mold, and some molds (thankfully, a minority) are toxic to all people. So the preferred solution is to fix the leak, and fully remove the mold. Problem is, if the mold is back inside a wall, you need to demo and replace drywall. Should it be under flooring, an even larger budget is indicated.
Caught an interesting article by our good friends at Cleaning and Maintenance Management, discussing issues that might not come readily to mind, particularly when one tries to cut cost - and corners - by avoiding demolition, using fogging and other chemicals to deal with the mold.
Some procedures involve "killing" the mold, and letting it set. Seems a reasonable solution. But, like any silver lining, there lurks a grey cloud within. A mold can be deactivated - rendered dormant - but will began growing again with a bit of moisture. Hard to tell if it is dead, or just dormant. Further:
"For many years, people have been tested by doctors for allergies, and through the testing process, determined to be allergic to mold. The process is called “prick-testing.” During this process, a mold spore is injected just under the skin and if the patient reacts with a raised bump of a certain size or itching, is the doctor may determine that person is sensitive to mold and probably has developed, or will develop, mold allergies. The spore is a dead, not viable, mold spore. What that simply means is that people react to mold whether it is dead or alive."
So - best to bite the bullet and remove the mold.